Controlling apparatus for refrigerating systems



A. D KARR Aug. 25, 193a CONTROLLING APPARATUS FOR- REFRIGERATING SYSTEMS Filed Dec. 12, 1934 2 Sheets-Sheet 1 INVENTOR. Alfrcd/D'Karr. BY 5 434; TORNEY A. D. KARR Aug. 25, 1936.

CONTROLLING APPARATUS FOR REFRIGERATING SYSTEMS 2 Sheet-Sheet 2 Filed Dec. 12, 1934 IN VEN TOR.

H15 ATTORNEY atete d CONTROlLiLlING APPARATUS FOR REFRTGERATING SYSTEMS Alfred B. Kai-r, Newarh, N. 3., assignor to Ingersoil-Rand Company, Jersey @ity, N. .L, a corporation of New Jersey Application December 12, 1934, Seriai No. 757L093 21 iClaimmS.

My invention relates to automatic regulating means; especially to controlling apparatus for a refrigerating system of the sort which includes an evaporator for a liquid refrigerant and means for carrying away the vapor formed therein.

An object of the invention is to insure full stability of the system .by temperature-actuated means that influence the operation of the devices for removing the vapor which the evaporator produces, particularly when a centrifugal compressor is employed for this purpose.

In a refrigerating system of this kind a liquid is cooled by transforming a portion into vapor,

the creation of which-extracts from the main body of the liquid the heat necessary to cause vaporization. The vapor is removed to a condenser and liquefied therein. To evacuate the vapor the use of a centrifugal compressor is quite advantageous, because such a compressor when coupled toan evaporator vessel is in great measure self-regulating and will run without pumping or surging down to a part load that is much less than heretofore; but at a very light load surging can still occur.

Another object of this invention is to eliminate the risk of surging altogether, preferably by differentially actuated temperature responsive 'means,,effective whenever very light loads are reached. a

-A further object of theinventi'on is to provide in a system of the kind mentioned, differentially operated appliances which enable suitable electrio circuits to be energized to render the stabilizing connections effective under predetermined conditions.

Yet another object of the invention is to provide means for preventing surging by lowering the discharge pressure of the evacuator under predetermined conditions.

A still further object is to raise the temperature within the evaporator and increase the suction pressure within the evaporator, to serve the same purpose. v

An additional object of the invention is to provide a refrigerating system comprising an evaporator from which vapor is withdrawn by a suitable member, such as a centrifugal compressor, and discharged into a'condenser, with a by-pass from the evaporator to the condenser, and means for opening said by-pass at low load so that part of the chilled refrigerant is withdrawn from the evaporator and admitted to the condenser to reduce the discharge pressure of the evacuator.

therein are returned to the evaporator, thereby conveying additional heat thereto and increasing the pressure therein to stabilize" the compressor at a time when pumping would otherwise occur. The objects and advantages of the invention 5 are fully set forth hereinafter in thedescription and the accompanying drawings, which present several embodiments of this invention. But I am a by no means limited to what is actually illustrated herein, because in practice many changes may be made without departing from the principle of the invention or exceeding the scope and spirit of the appended claims.

On the drawings, Figure 1 shows in outline a refrigerating system according to this invention, with electrical connections for controlling the compressor to prevent surging at low load,

Figure 2 indicates a second embodiment of the invention, and

Figure 3 shows a detail indicating another modification thereof. I

On the drawings the same numerals identify the same parts throughout. l

I indicate at i an evaporator which is a vessel to which water is admitted byway of. an interior nozzle or spray header 2, and an inlet or supply pipe 3. The nozzle 2 delivers the water in the form of jets or sprays; and the pressure in the evaporator 11 is kept low enough to cause some of the incoming waterat the prevailing temperature to be transformed into vapor at once, the remainder of the water falling down to the bottom of the evaporator and being withdrawn by way of a conduit t which carries it to the place where refrigeration is" needed. The outgoing water is several degrees lower in temperature than the incoming water, because the part which is vaporized takes heat therefrom and chills it. Only a small part of the water is vaporized, but the vapor thus formed is quite voluminous and must be removed from. the, evaporator by an evacuating device of. high capacity such as a'centrifugal compressor in a housing shown at 5. This compressor has preferably straight varies and its intake is in free communication with the upper part of the evaporator I and said intake may be permanently open and of substantially fixed area without a damper or other regulating appliance therein. The compressor 5 discharges through a permanently open outlet of constant 'size to a condenser 6. The compressor is rotated at a high but constant speed and in operation it regulates itself by taking more power at high loads and less power at low loads; and running with entire stability over a relatively great range,

because as the load drops the density of the vapor in the evaporator decreases, and the specific volume increases, with the same stabilizing effect The tendency to surge, however, is not entirely eliminated merely by the influence of conditions in the evaporator l, and surging or pumping will occur if the load is reduced far enough, unless special provision is made to obviate it.

For the purpose of doing away with surging altogether,. even at the very lightest loads, I connect the condenser 6 to the evaporator II above the level of. the chilled water therein through a by-pass l in which is a shut-off valve 8. This valve is opened and closed by a motor 9 which is energized by electric circuits controlled by two diiferentially arranged thermostatic elements it and ill in the condenser and evaporator respectively. These elements are in the form of bulbs containing a thermally responsive fluid and are connected by tubing l2 to expansible casings l3 and M respectively, as shown in Figures 2 and 3. Between these casings is a switch arm l5. The ends of the chambers toward the switch arm are movable, while the opposite ends are fixed, and the movable ends are each joined to the switch arm by rods It; The switch arm l5 has an insulated electrical contact H on its outer end which is connected to a supply wire I8. This contact ll engages one or the other of the contacts it at opposite sides thereof. One of these contacts is joined to a wire 2B and the other to a wire 2|. The wires l8, 2|] and 2| control the motor 9 and determine its direction of movement when actuated to open and close the valve ll. The switch arm I 5 is mounted upon a head 22 which slides on a rail 23 and can be adjusted by meansof a threaded screw 24 which passes through the head 22. This screw has an extremity 25 shaped like a ball received in a. suitable recess in a bearing 26. The screw can thus be turned freely, but cannot move longitudinally and as it is turned it will shift the head 22 back and forth along the rail 23. Normally the switch contact will be between the contacts l9 which will be suficiently close together, and one or both these contacts it are preferably adjustable to enable them to have correct working position.

The motor, for example, may have two oppositely wound field coils 21, connected in series with each other, one supplied by the wire 2|] and the other by the wire 2|. To the midpoint of. these coils I unite the movable armature coil 28, in series with a source of electrical energy 29 and the wire l8. Valve 8 may be a rotary valve with one projecting end carrying a rack 30, engaged by a gear 3| on the armature bearing the coil 28. ,The motor will be provided with limit switches to break the current through either field coil when the valve has reached the limit of its travel in one direction or the other.

With reference to Figure 1 suppose the switch arm to be in mid-position, and the circuits to the two coils 21 are open and the valve is shut. When, however, the temperature drops somewhat in the evaporator I the fluid controlled by the bulb H in the evaporator will-contract somewhat and the casing l4 shrinks a little, moving the arm l5 to the left to engage the adjacent contact IS in series with the conductor 2|. Current will now flow in the conductor 2| and the effect will be to energize the coil 21 connected thereto and actuate the motor armature and the aosaaoe valve 8 so as to open the valve. This type of motor-actuated valve is well known and need not be further described. As soon as the valve 8 opens, however, some of the water vapor can be returned from the condenser to the evaporator through the by-pass 1, thus increasing the intake of the compressor and the temperature and pressure thereof so that no surging occurs. In this way surging can be prevented entirely no matter how light the load on the system may become.

The valve 8 after opening will remain open, even after the contact H and the lefthand contact l9 separate. As soon however as the temperature in the evaporator rises again, the arm l5 will move to the right to close the circuit through the other coil 21 and then the motor will close the valve 8. The valve will now stay closed until conditions again move the arm I5 to close the circuit through the first coil 21.

In systems of. this kind, operation at part load is apt to be required for the greater part of the time, and stability in operation, even at very small loads, is desirable. My invention renders such light load operation quite effective, and no matter what working conditions may be, the compressor always runs smoothly.

In Figure 2 the arrangement is the same, except that the by-pass pipe I which contains the valve 8 runs from the condenser to the chilled water delivery conduit 33 of the evaporator at a point beyond the force pump 3t therein, and when this by-pass is opened, as the arm l5 closes the circuit through the conductor 2| to the motor,

' as before, chilled water is delivered to the vapors discharged by the compressor into the condenser to reduce the back pressure in the condenser. At the same time this water is warmed in the condenser, and returned with the condensate through a U-shaped pipe 35 to the evaporator, Ordinarily this pipe 35 returns to the evaporator only the condensed water vapor, but when the valve 8 opens, the chilled water going through the pipe 1' to the condenser and warmed therein, makes the amount of warmed water returning to the evaporator so large that the pressure and temperature in the evaporator increase to a suflicient extent to render surging impossible. The valve 8 will be closed again as soon as the temperature and pressure in the evaporator go high enough. This has the same effect as before to eliminate any risk of surging at light loads. The by-pass l is in effect connected to the evaporator adjacent the outlet and the pump 34 insures delivery of the chilled water to the place of use. The pipe 35 is also used in the system shown in Figure 1. Its two arms are long enough to prevent direct communication ever being established between the evaporator and the condenser.

Instead of the two contacts H I can substitute a resistance l9 arranged to be slidably engaged by the contact I! as shown in Figure 3. This construction will give modulated control of the valve 8 so that instead of being either wholly opened or wholly closed this valve can be moved to intermediate positions. The circuits through the wires 20 and 2| will be the same as before, but the motor 9 will contain circuits and limit switches as before so that this motor will effect movement of the valve to a greater or less extent in one direction or to a greater or less extent in the other direction according to the preponderance of electric current flowing through either the conductor 20 or 2|. When the contact I! is in mid-position the same amount of current will flow through the '5 means responsive to conditions in the evaporator aocaeot two conductors 20 and fl and the motor will be stationary. If, however, the arm it moves to the right or left, so that the contact l'l engages the resistance it to one side of its mid-point, the current from the source 29 through the wire ill will distribute itself to the wires 20 and M in inverse ratio to the amount of the two resistances into which the element I9 is divided, and more current will flow to'the wire 2|] at one time and more to the wire 2| at another. The circuits and limit switches associated with the motor 9 for giving this modulated control and enabling the motor armature to move to open the valve 8 either wholly or partly or in the opposite direction to close it wholly or partly, are well known and extensively used for example in'connection with dampers for heater fiues, hoists, etc., and can be similarly employed in connection with my invention. Hence, 7 they need not be described in detail here.

The by-pass I and the by-pass i may have a hand valve 36 so that by setting the valve 36, the flow through the by-pass can be throttled to the correct amount when the valve 8 opens.

Of course, I can utilize other means besides the motor 9 and the electrical and mechanical connections therefor to actuate .the valve 8. For example a device operated by compressed airto give modulated control can be connected to the valve 3.

While I have mentioned water as the refrigerant, my invention is obviously adapted for a systemwith a different refrigerating medium.

I claim: I V

1. In a refrigerating system, an evaportor, a centrifugal compressor to evacuate same, a condenser to which the compressor delivers, and means responsive to temperature conditions in the evaporator and the condenser to increase the pressure in the evaporator to stabilize the load on the compressor at light loads.

2. In a refrigerating system, an evaporator, an evacuator therefor, a condenser to which the evacuator delivers, and differentially controlled means to stabilize the load on the evacuator, said means comprising a conduit for introducing refrigerant' from the system into the discharge from the evacuator to the condenser.

3. In a refrigerating "system, an evaporator, an evacuator therefor, and means to stabilize the load on the evacuator by introducing refrigerant from the system into the discharge of said evacuator.

4. In a refrigerating system, an evaporator, an evacuator therefor, a condenser to which the evacuator delivers, and differentially controlled and the condenser to stabilize the load, on the evacuator, said means comprising a conduit for introducing refrigerant from the system into the discharge from the evacuator to the condenser. 5. In arefrigerating system, an evaporator, an evacuator therefor, a condenserto which the evacuator delivers, and means influenced by the temperature difference in the condenser and the evaporator to stabilize the load on the evacuator, said means comprising a conduit for introducing refrigerant from the system into the discharge from the evacuator to the condenser.

6. In a refrigerating system, an evaporator, an evacuator therefor, a condenser to which the evacuator delivers, and means responsive to conditions in the evaporatorand the condenser to stabilize the load on the'evacuator, said means comprising a conduit to introduce vapor from the condenser into the evaporator.

7. In a refrigerating system, an evaporator, an evacuator therefor, a condenser to which the evacuator delivers, and means influenced by temperature differences in the condenser and the evaporator to stabilize the load on the evacuator, said means comprising a conduit to introduce vapor from the condenser into the evaporator.

'8. In a refrigerating system, an evaporator wherein a liquid refrigerant is chilled, an evacuator for removing vapor from the evaporator,

a'condenser to which the evacuator delivers, and

means for introducing into the condenser part of the chilled liquid refrigerant from the evaporator to lower the pressure in the condenser and thereby stabilize the load on the evacuator.

9. In a refrigerating system, an evaporator, a compressor for removing vapor from the evaporator, said compressor having a compressionratio which varies with the load thereon, a condenser to which the compressor delivers, and means acting at predetermined conditions in the system to effect a decrease in the pressure in the condenser to stabilize the load on said compressor.

10. In a refrigerating system, the combination of an evaporator and a compressor for removing vapor therefrom, a condenser to which the compressor delivers, and means controlled by conditions in the system to cause the introduction of a chilled medium into the condenser at light loads to lower the pressure therein and thereby stabilize the load on the compressor.

I in the evaporator and the condenser to control electrical supply circuits for said motor, said circuits containing an adjustable switch connected to said elements.

12. In a refrigerating system, an evaporator, an evacuator for same, a condenser to which the evacuator. delivers, a bypass around said evacuator, a valve acting responsively to the difference between the temperature in the evaporator and the temperature in the condenser to open and close the by-pass, and a second valve to be set to determine the flowv through the by-pass when the first valve is opened. 4

13. The method of stabilizing the load on a compressor connected to an evaporator and preventing surging of the compressor, consisting in automatically causing by the action of the discharge of the compressor an increase in the temperature and pressure within the evaporator.

'14. In a refrigerating system, an evaporator, a condenser, a compressor for evacuating the evaporator and discharging into the condenser at a variable pressure, and means to simultaneously lower the pressure of such discharge and to raise the pressure in the evaporator during the operation of the compressor at light loads whereby the load on the compressor is stabilized.

15. In a refrigerating system, an evaporator, a compressor for evacuating the evaporator, a condenser to which the compressor delivers at a variable discharge pressure, and means responsive to differential conditions in the condenser and evaporator to simultaneously lower the pressure of such discharge and to raise the pressure in the evaporator during the operation of the'compressor at light loads whereby the load on the compressor is stabilized.

16. A refrigerating system comprising an evap orator, an evacuator therefor, a condenser to which the evacuator delivers, and means for automatically lowering the evacuator discharge pressure and raising the evacuator inlet pressure during the operation of the evacuator at light loads whereby the load on the evacuator is stabilized.

17. The method of stabilizing the load on a compressor connected between an evaporator and a condenser which comprises, under conditions of light loads, simultaneously lowering the pressure in the condenser and raising the pressure in the evaporator in response to difierential conditions in the evaporator and the condenser.

18. The method of stabilizing the load on a compressor connected to withdraw vapor from an evaporator and to deliver said vapor to a condenser at a variable discharge pressure, which comprises simultaneously lowering the pressure of such discharge and raising the pressure in the evaporator during the operation of the compressor at light loads.

19. The method of stabilizing the load on a compressor connected to an evaporator and a condenser to prevent surging of the compressor,

'whereby at light loads the evaporator pressure is raised in response to diflerential temperatures in the condenser and the evaporator.

20. The method of stabilizing the load on a compressor connected to an evaporator and a condenser to prevent surging of the compressor, whereby at light loads chilled refrigerant is admitted to the condenser to lower the temperature and pressure therein.

21. The method of stabilizing the load on a compressor connected between an evaporator and a condenser which comprises under conditions of light load conducting chilled refrigerant to the condenser and heating it therein to decrease the temperature and pressure in the condenser, then reconducting it to the evaporator to increase the temperature and pressure therein.

ALFRED D. KARE. 

